Lumen and lux measurements, why cant we all try to be on the same page?

For the record, im just sharing some observations and thoughts here. Im not claiming anything as fact. Nor is my purpose to point at anyone and saying their numbers are wrong. For those who feel affected, dot take this personal. I just want to get a discussion around this topic. If it can help measurements shared by BLF users to be more similar then nothing would be better than that.

The fact that the similar lights have slightly different readings, and that manufacturers who uses ANSI standards for measurements are all over the place does not help either getting everyone one the same page. But I think we, the enthusiasts should give it a shot.


The purpose of sharing measurements

What is the purpose of sharing measurements? Isnt it to be able to post numbers that are comparable with others? If so, would it not be beneficial that everybody were more on the same page? Would it not be beneficial for everybody to try and get closer to each other?


Lux:

When it comes to lux/kcd numbers its been quite clear for some time that the people with LX1330B have the highest numbers. At least that is what I have noticed. These numbers seems to some extent to have become close to the benchmark simply because so many of the people who often posts lux readings use one.

Typical difference in lux between a low reading meter and a LX1330B can be up towards 30%. In general though, it seems like peoples lux numbers are fairly close. Usually within 10-15%. Although, LX1330B usually have the peak numbers. That number is usually higher then most manufacturer ratings, and usually higher than calibrated expensive light meters.

Lumen:

There is mostly two camps here among people that often share numbers.

rdrfronty, Tom E, DBCstm, RMM and maybe others are example of people in the "high camp". Expect up towards 22% higher readings than most others. These people are among the main contributors of sharing lumen numbers on BLF. Most are into modified lights, so accuracy towards ANSI rated lights does not seem that important. Measuring 1200 lumen OTF from an emitter driven at 2,9-3A is also possible with the "high lumen calibration". Even though that is a bit doubtful compared to what you might expect from a Cree XM-L2 according to specifications. Thanks to copper mcpcb, and maybe extremely small OTF loss, it may be possible for all I know, but it certainly seems a bit too high for me.

Then there is the "ANSI camp". For these people getting a nice overall calibration compared to premium lights seems to have been of high priority and the baseline of calibration. Selfbuilt is one of the more known reviewers on CPF, he have used a lot of time calibrating his equipment for correct lumen readings. His numbers are basically the same as Fenix. Which is one of the manufacturers who posts numbers that seems quite consistent and reasonable (based on my personal observation and several others). I believe that some of the "top" reviewers and light buyers on BLF are typically within 7% of those numbers. _the_, johnnymac, HKJ, etc. I personally consider the work all these people have done with several hundreds of lights combined to be the benchmark. Usually when I see someone from another forum, theirs numbers usually are closer to the "ANSI camp". I dont see why this should not be the benchmark for everyone.

Some example issues:

People have a tendency to take numbers for a fact, or to be quite similar. Many are not aware that there can be up towards 30% difference in the numbers, and that 20% difference isnt that uncommon. This leads to issues when people want to compare different lights measured by different people.

In general, in some places its looked down upon to have too high numbers. Its often looked upon as cheating or bragging. On BLF, high numbers (posted by members) are usually met with "WOW, that is amazing. Great mod, etc). The higher the calibration, the more "wow". So if anyone wants to compare numbers with the people with the top numbers, you have to calibrate your gear for higher numbers. If someone with a "high calibration" sells lights, for many it will seem as if the modded lights are better then others, but really, the difference is just the calibration. At least that is what we have to assume, because the numbers are rarely comparable.

Its quite typical that someone compares manufacturer numbers. Say a TK61 with a modified TK61. A TK61 are rated at 1000 lumen. A modified might be measured to 1600 lumen. Many expect a 600 lumen/ 60% increase from stock. But they may not be aware that the guy who modded a light would measure the stock light to be 1200 lumen. Only making the increase 400lumen/33%. Quite a difference between a 33% gain and a 60% gain just because of a 20% difference in stock calibration.

Ive often heard about people who are not able to replicate numbers from other peoples mods. This may be due to issues with the mod, but in many cases, its just the calibration of the measuring equipment.


More example differences:

Here are some numbers for you. Please study them a little bit. All on Supbeam K50. There are many lights I could do a lot of funny numbers with. But K50 is one of the lights where many have shared numbers, and its fairly recent.

1600 Lumen - 140 kcd - Official numbers by Supbeam (Notice the high lumen number and "super low kcd")

1306 Lumen - 545kcd - JMpaul320 numbers from K50 modded vinh de-domed emitter and current increase (reference and more numbers here)

1450 Lumen - 188kcd - Selfbuilt numbers (Measured with calibrated lux meter, and the "typical ANSI lumen calibration")

1656 Lumen - 208kcd - (one of Tom E`s K50s. High lumen club + LX1330B light meter)

1642 Lumen - 218kcd - DBCstm stock K50 numbers. High lumen club + LX1330B light meter I assume. Quite similar numbers to Tom E, but even higher kcd)

Looking at JMpaul320 lumen numbers its obvious he belongs in the "ANSI rated lumen club". Despite the current increase, with losses from a de-domed emitter he still have the lowest lumen output, and its the only modified light. He probably uses LX1330B light meter. At least that is the meter he used before. His lux readings are always high, lumen readings seems to be typical ANSI numbers, although I have not studied them much.

If you ask DBCstm how many lumens his Supfire M6 with a FET driver have, he will say close to 5000 lumen.

If you ask JMpaul320 how many lumens his Securitying with FET driver (modified by RMM?), he will probably say about 3800 lumen. Sure, Dale`s M6 will have slightly more lumens with lower CRI U2 emitters and it probably have slightly less heat sag due to M6s better construction. But, it just shows to some extend the difference you can get by asking two people on pretty much the same light how the output difference is.


A possible improvement that I believe would benefit everyone:

The "high lumen club" adjusts down their lumen ratings with 7-15% (depending on how high their readings are compared to others.)

People with LX1330B (and other very high reading lux meters) adjusts down their lux readings with 2-7%.

Some last thoughts:

Sharing amp numbers, before/after mod, comparison with other lights always helps put numbers in a context. But in many cases, that is not done.

I think the purpose of sharing numbers is to contribute with data the is meaningful and helpful to others. If the numbers between different people have too large differences, it can be more misguiding than helpful. I believe that is often the case when "newcomers" check out numbers from "veterans" and assume they to some degree have comparable numbers and that these numbers can be compared with manufacturers of premium lights. Personally, I always have to "adjust" various peoples numbers in order to be able to get a better comparison. If the people with the "inflated numbers" would try and get on level with the "ANSI guys", then I think it would benefit everyone and make numbers more comparable and useful.

Wouldn't it be better if everyone tried to be on the same page?

Too many variables from what I’m seeing.

it is difficult to get perfectly accurate readings i agree. i do what most others do, is calibrate/calculate the Lux/Lumens reading based from testing ANSI rated known lights in my sphere.

Im not seeking perfection. I would just like to see that the gaps between people that seems to consistently be around 15-20% off. Based on posts by Tom E, im quite sure he have noticed this and is aware of the "issue". Its not hard to notice that certain guys are consistently much higher than others.

I can easily measure a light just based on ceiling bounce, and then easily choose if I want to be similar to the high lumen guys or the "ANSI lumen guys" despite all the variables. These days, I currently somewhere in between. Although if we could all meet with the "ANSI guys" that would be better for everyone IMO.

Most of the ANSI lumen guys are very close to each other. And then there is a gap to others.

For people who dont have a lot of comparison lights, premium lights, etc to use as reference, it may not be that easy to get a good calibration. Im certainly not claiming that. But even at my level (no integrating sphere), I easily notice the differences in both lux and lumen numbers. For the people who share numbers all the time, have measured xxx amount of various ANSI rated lights etc, it seems fairly easy to get closer to other..

I do not remember publishing any lumen values in my reviews. I have never had anything that I trust for precise lumen values. The "Estimated lumen" is not a measured value, but as it says an estimated value and it is based on the specified maximum lumens.

I know that in some of my comparison the scale looks like lumen, but I do never say it is lumen.

is there a cheap and easy to do possibility to get 2 fixed amounts of Lumens to “calibrate” our meters within some percent?

First point is to get a lumen meter, it is not cheap.

All the home made integrating devices might work more or probably less well. To test it: Try aiming the light in different directions into it, the lumen reading must be stable if it is a truly integrating device.

I have read and read over and over about this, on CPF and here. There's much better info over there. Basically, you will never be "within 15%-20%" with a home setup. The only true numbers will cost thousands of dollars. You can use home systems for "guesstimating" only and since there is no standard for these home systems, then there is no way to control the numbers, or the fact that they are all so far off from each other. The only way to find anything out would be to:

Go to a company that has the high priced system and have certain lights tested. Take your sphere with you to test your setup against theirs and make calculation adjustments to your readings, to get close to theirs.

Then send out those exact lights and exact batteries to others and have them do the same thing with their systems, till you had a base of a few people that were getting the same results consistently. Then it all has to be rechecked and verified once again every time you use the system, before trying a new light in it.

Not feasible and that is why I did not try to make a sphere. Even if you could make one that was close, it would cost thousands of dollars to buy a bunch of lights that have been ANSI qualified and it still wouldn't help, since you don't know what they used to power them at the time of testing, or the conditions of the tests. I don't listen to any of the numbers I see around here, because no one here has the correct setup to accurately test. They never will. If you really want good numbers, then you would have to buy a real integrating sphere and the software and accessories to do correct testing. before I ever believed any of the results. What we do around here is total guesswork and it's never really going to be accurate, no matter how much some people "believe" they are doing it right. Saying joe should cut his results by 15%, or john should do this, because he has xxx meter is just more total guess work and does not help solve the problems.

No one should be publishing their lux/lumens readings from any home meters or spheres, because there is no assurance at all, that they are even close to correct, so it's not good to even post them. Same for throw numbers. It's misleading for others. I don't mean that people are doing wrong on purpose, but it's still wrong. Unless it's lab checked and verified numbers, it's not relevant information. Better off just guesstimating from amps, if true amp readings can be gotten. Mine sure aren't.

Just me spouting off, I do a lot of it any more.

Was I was asking for is a “thing” that emits exact known Lumens…

by comparison it should be possible to get good numbers even on a cheap meter…

Lumen is difficult to measure, but lux is not nearly as difficult.

The main problem with lux is filtering: Lux is defined to follow the eyes sensitivity to colors, a silicium sensors does not have the same color sensitivity. This can be fixed with filtering, but good filters cost money, another way to fix it is with different calibrations, depending on light source, i.e. a meter that can be switched between different light sources does not have filtering, but only calibration for the light sources.

A meter like this is fairly good for lux:

any flashlight with ANSI rating

ANSI ratings mean absolutely nothing… just like UL/CSA/VDE labels. They are only as good as the paper they are printed on. Anybody can say their product is ANSI/UL/etc tested. Whether or not it actually is is pretty much a matter of trust. Even checking UL file numbers… those can be copied even easier than the product being counterfeited.

As far as lumen numbers are concerned… unless you have a decent sphere they mean absolutely nothing. Integrating ceilings, bathrooms, boxes, pluming pipes, eyeballs, or squirrel butts, etc are useless and misleading.

Lux numbers are a bit better… but I have seen cheap lux meters from the same maker, shipped at the same time, disagree by 30%.

Good thread. Good idea to have a standard BLF approach that members can try to implement, but not be beaten up for when they don't.

I've never tried to measure lumens as I don't even know where to start with a ceiling bounce (e.g. how far from ceiling with light, then with meter, what color and sheen paint on ceiling to use, popcorn or flat ceiling, etc, etc.).

For throw, I think it is good for folks to include the distance they took the measurement. I try to do that, but I haven't identified the meter in my reports.

For stock K50 V2, I measured 198kcd with the ubiquitous HS1010A (I think that's the model number).

No, manufacturers openly admit you will see +/- 7% from one exactly the same light to the next, in reality 10% difference isnt uncommon. You can buy a calibrated reference light (or build one and have it professionally certified at a lab) but an off the shelf flashlight, even from top tier manufacturers, is NOT ” a thing that emits exact known lumens”.

I think about this things often and came to no solution because like others said there are to many different variables.

I once hoped we would all “calibrate” our meters to the olight i6 which everyone bought and which seemed to have a output which is not sensitive to the used batteries…but it never happend.

A funny option would be constant current light which we would pass around and everyone can measure its lumen and lux. Maybe a man in the middle which gets submitted all the data and once everyone has it had it gets published. That would be fun to compare and I am sure we would see huge differences like racer said.

Another funny option would be a cardbox “integrating sphere” produced in china and send all over the world so that everyone has about the same…

An idea I have had for a while, inspired by a suggestion never carried out by match:

I am going to build a simple 18650 flashlight one of these days, lowly driven by a lineair driver (I have done this before, the output will be very constant and virtually independant of battery type or state) , then measure lux@1meter with my luxmeter and measure it in my integrating sphere and produce some djozz-lumens ;-) . Then I am happy to send it on a roundtrip around the world to other BLF-members, and have them measure their DBC-lumens, TomE-lumens or whoever is interested. And finally I receive it back and see if it still reads the same.

Using one and the same flashlight will at least reduce the number of variables (it will certainly not solve the problems related to the bad colour filters on the sensors of cheap luxmeters), but beside that I think it is a very fun thing to do :-)

You just beat me there posting about the pass-around flashlight, Werner :-)

I hope no one reading my posted measurements consider them the golden standard, or think I have some magical home setup that has a 0.0001% tolerance. NIST comes to me btw to calibrate their test equipment Smile.

What I don't like is the cherry picking of my posted #'s and emphasizing like it's typical. I can't explain all the differences, but many lights I've measured dead-on to manu specs or within an acceptable tolerance (maybe 3% is acceptable?), others lower, others higher. Sometimes I know I see variation in the positioning of the flashlight head on the glass of the PVC lightbox but I use it as precisely the same as possible, and I can't notice a consistent pattern that high throwers, high flooders, low lumens, or hi lumens get higher/lower readings. Do I or did I screw up sometimes? Sure I did - no doubt.

I do believe (from real, actual direct comparative measurements) that my $35 meter is accurate enough and compared very well to a much more expensive ExTech meter. In fact two of the $35 meters matched up well to an ExTech meter.

Also I have no idea where the notion or inference came from that we did not use ANSI rated lights to do the initial calibrations. Of course a multitude of ANSI rated lights were used. In fact there were probably at least as much or more ANSI rated lights used in the calibration process than others making the claim. Did every PVC based lightbox/meter combo get the same level of testing? - No. One setup was tested more extensively, others were built in the same design, then lights were shared, measured, compared, and calibration factors derived as a result.

However many ANSI lights are/were used by anyone, though, is not enough. There's too many variations from piece to piece, LED to LED, reflector to reflector, etc. in the so-called ANSI lights, noted and documented by many, like vinh and Michael at OSTS.

Now let's take a look at conservative/aggressive approach to this measurement dilemna. I believe my approach was conservative to the calibration, then aggressive to the measurements. Out of my collection of hot cells, I'll post the #'s on the cell that gave me the highest readings. How does this compare to the so-called ANSI lights? Well all depends on the approach the manufacturer, or contractor/facility the manufacturer hires to do the measurements. In theory there should be only one measurement - the accurate one, but that seems hard to obtain with almost any equipment. I think some manufacturers tend to take a conservative approach, fearing they will get in trouble by over-stating their "ANSI" claims, while under-stating is far less risk.

Passing one light around the world will help, but you really need a few representing different sizes and designs.

Here's a good example of readings I took on the NiWalker MM15, stock, on May 22nd:

MM15 clearly states "FL1 STANDARD" on their published #'s:

NiWalker my lightbox/meter (all in lumens done at 30 secs)

Mode 1: 6 11

Mode 2: 180 167

Mode 3: 450 483

Mode 4: 880 874

Mode 5: 1950 2013

Mode 6: 5233 5236

Throw: 19.6 kcd 17.2 kcd (measured at 5m)

Now I consider these dang close. Some might say mode 1 is way too far off, and it certainly is in percentage, but, you have to consider this is a high powered light using two MT-G2's. When these two LED's are cranked down that low, system tolerances andd variations are going to have a bigger effect, so this is not surprising to me.

In fairness, for Mode 6, I had 3 #'s written down, but this one was marked "cool", meaning the light was off long enough for temp. not to be a factor. The other readings wee 5,059 and 5,202.

Do we trust NiWalker enough to ensure they followed the ANSI FL1 standards to the letter when doing these tests? Me? No freak'n way... I don't trust any of them, be it Olight, Klarus, whomever. I know way too much about what goes on (or what doesn't).

Ohh - btw, what if NiWalker can't get P0 bin LED's, but found a source of Q0's, so they do their next batch run with Q0's. Do they re-test under the FL1 standard for the new batch run at a cost of $1,000's, maybe more? Do they update the shipping boxes with the new specs, and throw out the current inventory? Or maybe it's just for one batch, so do they pay for a special run of the shipping boxes, probably at another insane cost for a low volume? Oh sure they do - they only think of the customer, I'm sure... Smile

I recently purchased an HS1010A. I haven’t started any output tests but have completed throw numbers for all my lights.

I practiced for a while until I found I could get repeated, consistent results.

I had a few lights (Jacob A60 and two T08s) that I measured before and after mods. The mods I did on all three lights were pretty much standard affair, higher amp drivers, de-domed emitters, copper, resistance mods, etc.

I was surprised when I started comparing my numbers to similarly modded lights by others. With all 3 lights I found my stock numbers were a bit higher and modded numbers were significantly lower.

I did not expect in any way to be matching the kind of throw attained by some of the folks here but thought I would at least be in the ballpark.

I’ve decided as long as I can produce consistent results I can use my numbers to quantify my mods. That’s really all I wanted to do with the meter in the first place.